[amsat-bb] Re: WAS Re: AO-16 report from Copenhagen
Tom Clark, K3IO
k3io at verizon.net
Wed Jan 23 22:14:24 PST 2008
Mark, N8MH noted:
> The 437.024 transmitter antenna configuration on AO-16 is Left Hand Circular
> polarity (LHCP). The receiving antenna on the bird is a 1/4 wave vertical
This whip operates against the body of the spacecraft as a "ground
plane"; however the spacecraft body is a cube 22 cm on a side (you can
see a picture at
This is about half of the quarter-wavelength you'd like to see for a
proper ground reference, so the actual pattern undoubtedly has some
> The fading is quite dramatic, which means the bird is spinning/tumbling, or
> some combination. We could never hear this before on AO-16 when it was
> transmitting its normal PSK signal, since we didn't hear the effect of fading
> on the uplink in this mode. Now we hear it, loud and clear!
> It does take an uplink signal that is pretty close to on frequency (145.820).
> Adjusting for Doppler is helpful thing on the uplink.
The receiver has a 15 kHz wide crystal filter with sharp skirts. So if
your NBFM xmtr is set with a ±5 kHz deviation, you may well find your
signal hitting the filter "walls". You may get better performance if you
crank the deviation back a bit.
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